The Study Of The Phosphate-bonded Quartz Investment

Objective This pilot study was to form a phosphate-bond investment used for support of cobalt-chromium alloy according to the foreign investment, and to replace the foreign investment material in order to low the price.Materials and methods This study was divided into three parts as following:Part I : The composition, structure and properties of the phosphate-bonded quartz investment.Mix the powder of the four foreign investment and corresponding investment liquid in accordance with the special proportion. And model them. Then their chemical compositions, microstructure and basic physical properties were tested. The basic physical properties include apparent porosity, bulk density, compression strength, setting expansion and thermal expansion.Part II : The influence to the basic physical propertied of the investment after its composition or particle size distribution waschanged.After the composition or particle size distribution of the investment was changed, apparent porosity, bulk density, compression strength, setting expansion and thermal expansion were tested.Part IE: Casting accuracy of investment used for support of cobalt-chromium alloy was tested.The foreign investment used for support of cobalt-chromium alloy islooked as opposite group, and our own investment is the experimental group. Then their castability value, marginal fit, casting dimension and surface roughness were tested. ResultsPart I: Phosphate investments consist essentially of two main groups of ingredients, fillers and binders. The fillers usually consist of quartz and cristobalite. The binders are essentially basic MgO and NH4H2PO4 By means of SEM, it is found that there is a lot of NH4MgPO4 6H2O crystal. Its thermal expansion is the result of SiO2 translation from type to a type. Its physical properties are closed to the composition and structure.Part II .?The composition or particle size distribution of the investment has great influence to its basic physical propertied.Part HI: The experimental group had no significant differences in castability value, casting dimension, surface roughness, compared with the opposite group. But there was significant difference in marginal fit, which will be improved in the further research.Conclusion Our own investment used for support of cobalt-chromium alloy can be basically used in clinic, which will be improved in the further research.